It has been known for some time that Benign Prostatic Hypertrophy, abbreviated to BPH, which is the result of natural enlargement of the periurethral glands of the prostate more or less inevitably leads to compression of the urethral canal preventing the patient from urinating normally. To remedy this problem, resection, more particularly periurethrally, using a resecting device, is the safest and most reliable method recognised worldwide as being the standard treatment of BPH.
More recently it was proposed by HARADA et al., in Urology, in December 1985, volume XXVI, no. 6, pages 572 to 576, to perform transurethral thermal resection of the obstructive BPH tissues by inserting a transurethral probe means comprising an antenna emitting microwaves at a frequency of 2450 MHz. Said thermal treatment succeeds in coagulating the prostate tissues starting with the urethral canal, the maximum temperature attained can reach almost 1000.degree. C. This procedure used to require a general anaesthetic on account of the impossibility for the patient to bear the pain caused by the thermal treatment and also the permanent fitting of an urethral catheter for several weeks whilst waiting for the open periurethral wound to heal. It is indicated that diuresis persisted for beween 30 and 60 days in the majority of cases. This method enables full devascularization of the prostatic tissues to be performed and is considered to be of interest in the initial phase before proceeding with prostate resection which is usually a delicate operation on account of profuse bleeding. This method has never found practical application.
The document Medical Tribune of Mar. 31 1988, volume XXIX, no. 9, pages 1, 4, 11, 13 and 14, likewise describes a transurethral probe comprising several microwave-emitting antennas made fast externally with a Foley catheter for treatment of BPH by hyperthermia at a temperature not exceeding 45.degree. C. so as to heat the central part of the prostate therefore necessarily involving the wall of the urethra. Moderate heating to a hyperthermia temperature is recommended according to a treatment procedure of between 5 and 10 one-hour sessions, once or twice a week, which is extremely traumatic for the patient. Further, due to the moderate temperature, which is that of hyperthermia, usually from 42.degree. to 43.degree. C. in the tissues to be treated, said temperature is inadequate to bring about histological modification to the BPH tissues which are not by nature malignant or cancerous. Hyperthermia has always been advocated for destroying cancerous cells which are less resistant to heat than healthy cells. However, BPH, which is the result of natural enlargement of the periurethral glands of the prostate, does not comprise cancerous cells. In this document, the transurethral probe is held in place in the urethra by the presence of a front balloon inflated in the bladder coming to be locked in the neck of the bladder.
Technomed document FR-A-2 639 238 also discloses an apparatus for the surgical treatment of prostate tissues causing destruction thereof, using an urethral probe comprising a microwave antenna, said urethral probe being provided with thermal protection means for the urethra and comprising more particularly cooling means. Thanks to this combination of an urethral probe with irradiation heating by microwaves and cooling by conduction, an effective treatment has been made possible, quite unexpectedly, in a single one-hour session, without anaesthetic, the cold having an anaesthetic effect on the nerves of the urethral wall, and without side effects such as tissue loss or retrograde ejaculation. The apparatus in accordance with said patent, marketed by Technomed under the name of Prostatron.RTM. has met with resounding commercial success, more particularly, thanks to its ability to perform necrosis of intraprostatic tissues while preserving the urethral wall intact, a result which the prior art has not been able to achieve.
The prior art is particularly suitable for the treatment of relatively large prostates for which maximum obstruction is the consequence of hypertrophy of the transition region starting in the periurethral glands and ending at a point midway between the bladder neck and the Veru montanum.
However, it happens that, in a number of cases, a non-negligible part of which is made up of prostates with a volume not exceeding 30 cm.sup.3, the cause of the obstruction of the urethral canal does not lie primarily in the consequence of hypertrophy in the transition region starting in the periurethral glands, but, quite the contrary, in the hypertonicity of the muscles of the bladder neck and the intraprostatic sphincter. Likewise, in the case of prostates with a volume greater than 30 cm.sup.3, examples can occur where the maximum obstacle is located at the level of the bladder neck whose hypertonicity also plays a part in obstructing the urinary tract.